Responses
If you remember kiriya san was thinking about how to get out from the situation, and considering that he and yuri's eyes met earlier, he was thinking the possibility that yuri will be there sooner or later.. and the man will be save.. But.. coming back the situation, the action of kiriya san suiciding is being hurried thus he is certain that he needed to go because he's friend will certainly die... i also think that the way he tried to beg for the offender to just talk it out was a way to make it longer before you know what
So if he doesn't jump friend dies
If he jump he dies and friend die after
Doesn't make sense